The present invention relates to a method of weld repairing of a section of a metallic cylindrical member, and more specifically, the weld repairing of a turbine or generator component, such as a rotor or extension shaft having a keyway therein, to remove surface defects or deviations.
During use, sections of various metallic cylindrical components of turbines and generators, such as rotors and the like, can incur surface defects or deviations of a superficial depth in the surface. Typical examples are shallow cuts, shallow surface indentations, fretting, or loss of fit with a mating part (such as an oil pump runner). A recent development for use in the repair of such metallic cylindrical components has been to weld repair the same. Shaft weld repairs to correct such defects require a continuous surface on the component. Such components are highly stressed parts, and the welds must be of the highest integrity.
Examples of weld repair of turbine or generator components are described in U.S. Pat. No. 4,663,554, U.S. Pat. No. 4,893,388, U.S. Pat. No. 4,897,519 and U.S. Pat. No. 4,903,888, all of which are assigned to the assignee of the present invention. The contents of these four patents are incorporated by reference herein.
There is, however, always a risk that residual stresses, resulting from a relatively thick weld-building on a shaft, for example, where the weld build-up is large relative to the shaft diameter, can cause "bowing" distortion of the shaft. Thus, as a general principal, it is described to keep the thickness of the weld small compared to the shaft diameter, so as to assure a safer and more predictable repair.
In those sections where the metallic cylindrical component has a slot or keyway, to tie the shaft into another component by use of a key fitted into the keyway, a particular problem exists in weld repair of the same when a welding machine is used that requires a continuous surface, or a common surface 360.degree. about the shaft. In previous repairs of such a section containing a keyway, since a continuous 360.degree. surface was required for welding, it was necessary to machine away the surface containing the defects and the keyway to a degree that the shaft was of a much smaller diameter than the initial diameter and completely remove the keyway. Such machining resulted in a small diameter shaft and a thick weld build-up, after weld repairing such that the weld becomes a large percentage of the cross-section of the shaft.
It is an object of the present invention to provide a method of weld repairing a section of a metallic cylindrical member containing a keyway without the need to machine out the keyway from the member.
It is another object of the present invention to provide a method of weld repairing a section of a metallic cylindrical member containing a keyway, such that the thickness of the weld is substantially reduced as compared to prior art weld repaired such sections.